I have other 12 song cds with a lower mb than this why is this one so much?

Are you reading that from the CD itself? Or is that what you imported?

When i put it on my itunes it said 77.3 megabytes

After or before you imported? Is that the CD information or what you got out of it? Once you upload it should come out to somewhere a little less than half of that.

Before i imported it it showed that number at the bottom. but now that i just checked alone its only 15 mb. without cd in.

Yeah, the CD holds a lot of information on it. Judging by how you set your import settings, it can reach much higher than 15 mb on your computer if you get 320 kbps, or FLAC.